Biodegradable resins begin to degrade in several weeks by actions of enzymes produced by microorganisms living in nature in a case where the biodegradable resins are placed in soil, sea waters, or inside the body of animals, and disappear during a period of about an year to several years. Therefore, in recent years, utilization of the resins is being remarked.
For example, Patent Publication 1 discloses a method of obtaining a biodegradable resin composition having favorable crystallization velocity and transparency, in which heat treatment is carried out by melt-kneading at a particular temperature a biodegradable resin, a plasticizer, and a crystal nucleating agent which is an aliphatic compound having two or more groups of at least one selected from the group consisting of an ester group, a hydroxyl group, and an amide group in one molecule. The above-mentioned crystal nucleating agent is exemplified by fatty acid esters such as fatty esters and hydroxyfatty acid esters; fatty amides such as hydroxyfatty acid monoamides, fatty bisamides and hydroxyfatty acid bisamides; and metal salts of aliphatic acids such as metal salts of hydroxyaliphatic acids;